Board Mounted Electrical Connector

ABSTRACT

A circuit board mounted connector is equipped with an insulative housing, which holds a plurality of rows of contacts and is mounted on a circuit board. Each contact has a contact portion, for contacting another connector; and a leg portion, which is connected to the circuit board. Each leg portion has an extending portion that extends from a rear wall of the insulative housing; a flexible portion, which is formed continuously with the extending portions; and a linear portion that extends in a direction substantially perpendicular to the circuit board from the flexible portion and is connected to an aperture of the circuit board. Of the plurality of rows of contacts, at least the row closest to the circuit board has extending portions that extend away from the circuit board, up to the flexible portions. The linear portions of each of the leg portions are partially tin plated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 11/129,779; filed May 16, 2005, which claims the benefit of thefiling date under 35 U.S.C.§ 119 (a)-(d) of foreign application JP2004-144454, filed May 14, 2004.

FIELD OF THE INVENTION

The invention relates to a board mounted electrical connector and moreparticularly the invention relates to a board mounted electricalconnector, of the type in which leg portions, of contacts utilized inthe electrical connector, extend outwardly from the rear wall of ahousing, are bent such that they are substantially perpendicular to thecircuit board, and are receivable in apertures of a circuit board.

BACKGROUND

There is known a conventional board mounted electrical connector, asdisclosed in Japanese Unexamined Patent Publication No. 9 (1997)-069371.This connector comprises contacts, which are arranged in three rows, andan insulative housing, for holding the contacts. Each of the contacts ofthis connector comprises a contact portion, which has an axissubstantially parallel to a circuit board, on which the housing ismounted; and a leg portion, which extends outwardly from the rear wallof the housing, then extends in a direction perpendicular to the axis ofthe contact portion, and is received in apertures of the circuit board.Each leg portion comprises an extending portion that extends away fromthe circuit board from the rear wall of the housing; a flexible portion,which is formed continuously with the extending portion; and a linearportion that extends substantially perpendicular to the circuit boardfrom the flexible portion.

In board mounted electrical connectors, rates of thermal expansiondiffer between insulative housings that form the connectors, and circuitboards that the insulative housings are mounted on. Due to thedifference in the rates of thermal expansion, degrees of expansion andcontraction of parts due to changes in temperature differ. As a result,stress is generated at connecting portions (soldered portions) betweencontacts and the circuit board, which may cause the soldered portions tocrack. For this reason, the known electrical connector has adopted theextending portions that extend away from the circuit board, therebyextending the entire lengths of the leg portions. The extended lengthsof the leg portions absorbs dimensional differences due to expansion andcontraction of parts, in an attempt to reduce the stress applied on theconnecting portions between the contacts and the circuit board. As aresult, the dimensions of the leg portions are enabled to be madelarger, even if spacing between the contacts and the circuit board aresmall. Accordingly, low profile, high density mounting of connectors oncircuit boards is capable of being realized.

Normally, the leg portions of contacts are plated with solder thatcontains lead. This is because the leg portions are soldered to thecircuit board with solder that contains lead, and if the leg portionsare plated with solder that contains lead, the connection properties arefavorable. As a result, there is a possibility that the lead willpollute the environment during production of the electrical connector,or upon disposal of the connector. In the case that the entirety of theleg portions is plated with a metal such as tin that does not containlead (lead free solder), the possibility of environmental pollution isdecreased. However, whiskers (phenomena in which needle like crystalsare generated on the surface of the plating) may be generated at theflexible portions of the leg portions. The cause of these whiskers isinternal stress, which is generated in the contacts, and the whiskersare likely to appear at the flexible portions. If whiskers aregenerated, they cause adjacent contacts to short, thereby causing aproblem that desired electrical connection properties cannot beobtained.

SUMMARY

The present invention has been developed in view of the abovecircumstances. It is an object of the present invention, among others,to provide a board mounted electrical connector, which is capable ofrealizing low profile, high density mounting, while preventingenvironmental pollution by lead, and preventing the generation ofwhiskers.

The board mounted electrical connector of the present inventioncomprises contacts; and an insulative housing for holding the contactsin a plurality of rows. Each of the contacts has a contact portion forcontacting another connector; and a leg portion that protrudes outwardlyfrom a rear wall of the insulative housing, to be connected to a circuitboard. Each of the leg portions has an extending portion that extendsfrom the rear wall of the insulative housing; a flexible portion, formedcontinuously with the extending portion; and a linear portion thatextends from the flexible portion toward the circuit board substantiallyperpendicular thereto, to be inserted through apertures in the circuitboard and connected thereto. At least the contacts in the row closest tothe circuit board have extending portions that extend from the rear wallof the insulative housing in a direction away from the circuit board, upto the flexible portions. The linear portions of each of the legportions are partially tin plated meaning that a portion or the entiretyof the linear portion is tin plated, and that other portions of the legportion, such as the flexible portion, are not tin plated.

Here, the tin plating may be plating with pure tin, or with tin alloysthat do not contain lead, such as tin-copper alloys and tin-bismuthalloys.

The linear portion may be perfectly linear. Alternatively, the linearportion may have a slightly swollen shape, to impart elasticity in thedirection perpendicular to the axis thereof. The swollen portion may beconfigured to be connected with the circuit board.

The flexible portion may be intentionally formed with an arcuate portionhaving a large radius. Alternatively, the flexible portion may have asmall diameter arcuate portion, formed by simply bending a linear legportion.

According to the first board mounted electrical connector of the presentinvention, at least the contacts in the row closest to the circuit boardhave extending portions that extend from the rear wall of the insulativehousing in a direction away from the circuit board, up to the flexibleportions. In addition, the linear portions of the leg portions arepartially tin plated. Therefore, low profile mounting of the electricalconnector is realized, while preventing environmental pollution by lead.Further, because tin plating is not performed at the flexible portions,generation of whiskers is also prevented.

According to the second board mounted electrical connector of thepresent invention, the extending portions extend from the rear wall ofthe insulative housing in a direction away from the circuit board, up tothe flexible portions. In addition, the linear portions of the legportions are partially tin plated. Therefore, environmental pollution bylead is prevented, as well as generation of whiskers, because tinplating is not performed at the flexible portions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams of board mounted electricalconnectors according to a first embodiment of the present invention,wherein FIG. 1A illustrates a case in which the entire lengths of legportions are relatively short, and FIG. 1B illustrates a case in whichthe entire lengths of leg portions are relatively long.

FIG. 2 is a schematic diagram of a board mounted electrical connectoraccording to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Hereinafter, embodiments of the board mounted electrical connector(hereinafter, simply referred to as “connector”) according to thepresent invention will be described in detail with reference to theattached drawings. FIG. 1A illustrates a case in which the entirelengths of the leg portions are relatively short, and FIG. 1Billustrates a modification, in which the entire lengths of the legportions are relatively long. First, a description will be given withreference to FIG. 1A. The connector 1 generally includes an insulativehousing 2, to be mounted onto a circuit board 14, and a plurality ofcontacts 6 (6 a, 6 b), which are held by the insulative housing 2. Anengaging recess 8, for receiving another connector (not shown), isformed in the insulative housing 2.

The contacts 6 are constituted by upper contacts 6 a and lower contacts6 b. Both the upper contacts 6 a and the lower contacts 6 b are arrangedin directions perpendicular to the surface of the drawing sheet of FIGS.1A and 1B. In the first embodiment, the upper and lower contacts 6 arearranged in two rows. However, three or more rows of contacts may beprovided. Each of the contacts 6 comprises a holding portion 10, whichis inserted through a rear wall 4 of the insulative housing 2 and heldthereby by being press fit or the like; a contact portion 12 thatextends linearly forward, that is, toward an engagement direction fromthe holding portion 10, to contact contacts of another connector (notshown); and a leg portion 16 that extends rearward from the rear wall 4to be connected with the circuit board 14. Note that the insulativehousing 2 may be fixed to the circuit board 14 by only the leg portions16. Alternatively, other fixing means, such as screws (not shown), maybe employed in addition to the leg portions 16, to fix the insulativehousing 2 to the circuit board 14.

Each of the leg portions 16 a of the upper contacts 6 a comprises: anextending portion 18 a that extends from the rear wall 4 in a slightlyupwardly inclined direction; a bent or flexible portion 18 b, which isformed continuously with the extending portion 18 a; and a linearportion 18 c that extends downward from the flexible portion 18 b, in adirection substantially perpendicular to the circuit board 14. Thelinear portion 18 c is inserted through an aperture 20 correspondingthereto of the circuit board 14, and is soldered to the circuit board 14with a lead free solder, such as tin-copper solder.

Meanwhile, each of the leg portions 16 b of the lower contacts 6 bcomprises: an extending portion 22 a that extends from the rear wall 4in a sharply upwardly inclined direction; a bent or flexible portion 22b, which is formed continuously with the extending portion 22 b; and alinear portion 22 c. The differences between the leg portions 16 b andthe leg portions 16 a are that the entire lengths of the lower legportions 16 b are shorter than those of the upper leg portions 16 a andthat the extending portions 22 a extend in a direction away from thecircuit board 14 at a relatively acute angle. The extending portions 18a and 22 a extend in directions away from the circuit board in order toincrease the lengths of the leg portions 16 a and 16 b from the rearwall 4 to the circuit board 14 as much as possible within a limitedmounting surface area. Thereby, the difference in degrees ofexpansion/contraction, due to the difference in the rate of thermalexpansion between the connector 1 and the circuit board 14, can beabsorbed. Accordingly, the amount of force exerted on the connectingportions among the circuit board 14 and the linear portions 18 c and 22c is reduced, thereby preventing cracks from forming at solderedportions 29 of the connecting portions.

What is important to note here is that the leg portions 16 are partiallytin plated. The linear portions 22 c of the leg portions 16 b of thelower contacts 6 b are tin plated. That is, the leg portions 16 b aretin plated from the tips 22 d thereof up to the beginning of theflexible portions 22 b. The tin plated portions are indicated byhatching in FIGS. 1A and 1B. The leg portions 16 a of the upper contacts6 a are tin plated from the tips 18 d thereof up to the same heights asthe tin plated portions of the linear portions 22 c of the leg portions16 b. That is, the leg portions 16 a are tin plated up to the positionindicated by arrow 24 in FIG. 1A.

The leg portions 16 a of the upper contacts 16 a may be tin plated alongthe entirety of the linear portions 18 c, up to the flexible portions 18b. That is, the leg portions 16 a may be tin plated up to the positionindicated by arrow 28 in FIG. 1A. Tin plating is administered on eitherthe entirety or a part of the linear portions 18 c and 22 c, but not onthe flexible portions 18 b and 22 b. Therefore, there is no possibilitythat whiskers will be generated on the flexible portions 18 b and 22 b.

Note that the tin, which is used as the plating material, may be eitherpure tin or a tin alloy that does not contain lead. For example, atin-copper alloy lead free solder may be plated, and soldering may alsobe performed using the tin-copper lead free solder. In this case, thesoldering properties are favorable, and manufacturing costs can also besuppressed. Alternatively, plating may be performed using a tin-bismuthalloy lead free solder.

Next, the manufacturing steps of the connector 1, through the point whentin plating is performed, will be described. The contacts 6 are punchedfrom a metal plate of copper alloy or the like by stamping. Then, theentirety of each of the contacts 6 is nickel plated. Thereafter,portions of the leg portions 16 of the contacts 6 are tin plated for apredetermined length from the tips 18 d and 22 d thereof. That is, theleg portions 16 are tin plated up to the position indicated by theaforementioned arrow 24, or in the case of the leg portions 16 a, up tothe position indicated by the arrow 28. Next, the contacts 6 are bentinto predetermined shapes then press fit into the rear wall 4 of theinsulative housing 2, to construct the connector 1. Alternatively, thecontacts 6 are pressed into the rear wall 4 of the insulative housing 2,then bent into their predetermined shapes, to construct the connector 1.

Next, an alternate connector 40, which is a modification of theconnector 1, will be described with reference to FIG. 1B. Note that inthe following description, elements which are the same as thoseillustrated in FIG. 1A will be described with the same referencenumerals. In addition, the inner structure of the connector 49 is thesame as that of the connector 1, and therefore a description thereofwill be omitted. The connector 40 differs from the connector 1 in thatthe entire lengths of leg portions 56 (56 a, 56 b) of contacts 46 (46 a,46 b) are longer. For this reason, the connector 40 is better able toabsorb stress generated at the connecting portions, that is, thesoldered portions 29, between the connector 40 and the circuit board 14,due to differences in rates of expansion/contraction thereof.

Accordingly, extending portions 58 a of the upper contacts 46 a extendsubstantially parallel to the circuit board 14. The angle, at whichextending portions 62 a of the lower contacts 46 b extend away from thecircuit board 14 from a rear wall 44 of an insulative housing 42, issmaller than that of the extending portions 22 a of the connector 1.Linear portions 58 c and 62 c of the leg portions 56 of the connector 40are partially tin plated, in the same manner as in the connector 1. Tinplating is performed on the linear portions 58 c and 62 c, whileavoiding bent or flexible portions 58 b and 62 b, in the same manner asin the connector 1. Therefore, a detailed description will be omitted.

In the connectors 1 and 40 illustrated in FIGS. 1A and 1B, the lengthsof the leg portions 16 and 56 may be extended, even if the distancebetween the holding portions 10 and bottom surfaces 30 of the connectors1 and 40 are short. This is accomplished by forming the extendingportions 18 a, 22 a, and 62 a such that they extend away from thecircuit board 14. Therefore, if the circuit board 14 is placed at theposition indicated by reference numeral 14′, low profile mounting of theconnectors is enabled. Accordingly, the mounting surface areas of theconnectors 1 and 40 can be kept small, while enabling low profilemounting of a plurality of connectors at high density on the circuitboard 14.

Next, a connector 80, according to another embodiment of the presentinvention, will be described with reference to FIG. 2. FIG. 2 is aschematic view of the connector 80 according to the second embodiment.The connector 80 of the second embodiment differs from the connectors 1and 40 illustrated in FIGS. 1A and 1B in that extending portions 98 aand 102 a, of leg portions 96 (96 a, 96 b) of contacts 86 (86 a, 86 b)which are held by an insulative housing 82, extend substantiallyparallel to the circuit board 14. The shape of these leg portions 96 issuitable for cases in which there is ample space for long leg portions96, or for cases in which the difference in rates of thermal expansionbetween the insulative housing 82 and the circuit board 14 is small. Inthis case as well, linear portions 98 a and 102 c may be partially tinplated, at the portions indicated by hatching in FIG. 2. This partialtin plating may be performed up to bent or flexible portions 98 b and102 b, in the same manner as in the case of the connectors 1 and 40illustrated in FIGS. 1A and 1B.

In the case of the connector 80 illustrated in FIG. 2, the extendingportions 98 a and 102 a are parallel to the circuit board. Therefore, itis difficult to minimize the mounting surface area of the connector 80,and also difficult to realize low profile mounting of the connector 80.However, environmental pollution by lead, and formation of cracks atsoldered portions (connecting portions between the connector 80 and thecircuit board 14) can be prevented.

1. A board mounted electrical connector comprising: an insulativehousing having a rear wall for receiving contacts in a plurality ofrows; the contacts having a contact portion for contacting anotherconnector and a leg portion that protrudes outwardly from the rear wallof the insulative housing to be connected to a circuit board; each ofthe leg portions having an extending portion that extends from the rearwall of the insulative housing, a bent portion formed continuously withthe extending portion, and a linear portion that extends from the bentportion toward the circuit board substantially perpendicular thereto,the linear portion having a tip to be inserted through apertures in thecircuit board and connected thereto; and each of the leg portions havingtin plating applied solely to the linear portions thereof such that thegeneration of whiskers caused by internal stress on the leg portions isprevented.
 2. The board mounted electrical connector of claim 1, whereinthe linear portions of each of the leg portions are plated with a tinalloy.
 3. The board mounted electrical connector of claim 1, wherein thecontacts are nickel plated.
 4. The board mounted electrical connector ofclaim 3, wherein the tin plating is applied over the nickel platedcontacts.
 5. The board mounted electrical connector of claim 1, whereinthe plurality of rows include an upper row and a lower row, the linearportion of the contacts of the upper and lower rows having tin platingapplied thereto from the tips thereof to the same height.
 6. The boardmounted electrical connector of claim 1, wherein each of the linearportions is entirely tin plated from the tip to a beginning of the bentportion.
 7. An electrical connector comprising: an insulative housinghaving a rear wall; a plurality of contacts arranged in rows along therear wall, each contact having a contact portion extending forwardlyfrom the rear wall, and a leg portion extending rearwardly from the rearwall, the leg portion comprising an extending portion extending from therear wall, a bent portion formed continuously with the extendingportion, and a linear portion that extends from the bent portion to atip; and tin plating applied solely to each linear portion such that thegeneration of whiskers caused by internal stress on the leg portions isprevented.
 8. The electrical connector of claim 7 wherein the linearportion is disposed substantially perpendicular to the extendingportion.
 9. The electrical connector of claim 7, wherein the tin platingcomprises a tin alloy.
 10. The electrical connector of claim 9, furthercomprising nickel plating on the contacts.
 11. The electrical connectorof claim 10 wherein the tin plating is applied over the nickel plating.12. The electrical connector of claim 7, wherein the rows include anupper row and a lower row, the linear portion of the contacts of theupper and lower rows having tin plating applied thereto from their tipsa similar distance toward their respective bent portions.
 13. Theelectrical connector of claim 7, wherein each of the linear portions isentirely tin plated from the tip to a beginning of the bent portion.